Rough Idle

H3 Specific Information

Rough Idle

Postby KGFORD » Sat Nov 21, 2009 8:41 pm

Hello every one, been lurking here for some time but finally need eveyones help.

I bought a 2006 H3 with 87k on the odometer. Had it for a little over a two monhs now and absolutely LUV this thing.

Anyway, seemsit has developed and intermittent rough idle over the last two weeks since I have been out of town on bussiness.
Got home and took it for a ride today and sure enough, confirmed what my wife told me. Initially the rough idle was very mild and
intermittent. Noticeable under 1500RPM's and smoothed out afterwards. No check engine light present and no error codes stored
after having it checked at Autozone.

I decided to try and throw some plugs into the car and became aware of my 1st problem. Bought all new Autolite Platinum Plugs
(AP 5263) and could not find the Gap setting for these plugs, or any other plugs off the internet. Had to assume that they where
pre-gapped and checked them at .045 to .046 Checked the original plugs and they appear to be gapped the same. The original
plugs are AC Delco 41-981 12599232 and they all appear to be burning clean. Replaced with new Autolite Platinum and H3 and
now seems to have the same rough idle, maybe more pronounced. After a 5 min test drive the CEL finally came on and I drove to
Autozone where they where able to confirm "Cyl 2 miss fire" I decided to buy a new Coil-Ignition for #2cyl and it turns out they have
nothing listed/available for the H3.
We looked up the same part for a 3.5L Colorado engine and it shows OEM PN# 8-12568-062-0 The one they sell is made by Duralast
PN# C1395 $62.99 My 1st question is if these two parts are the same for the H3 and the Colorado?

My 2nd question is more drawn out........ Why did the CEL not come on with the original plugs when it was obvious there was a missfire?
I am aware of the bad Cyclinder heads with poorly heat treated valve guides but this vehicle has 87k on it? also if it where a bad valve guide
would it not have a consistent rough idle at any RPM and wouldnt the #2 Cyl Spark plug be some what fowled compared to the others?

I am afraid to take the vehicle into the Dealer because I hate to be lumped into some " Ah yea, they had a batch of bad cylinder heads,
that will cost you $3000.00 thanks"

Wanted to do a Compression check but not even sure how to do that on this car since the plugs are under the air box. Not even sure what
the compression values should be? I am hoping that all I have to do is replace the Coil ignition with the same part as the one
for the Colorado but I would hate to buy the wrong part and cause myself even more confusion?

If the MAS was dirty the idle would be erratic but not feel like a miss fire? If the Throttle body was dirty and sticking then I would feel a hesitation
while accelerating and the idle would stay high while decelerating which is not the case.....

any input or feed back would be GREATLY appreciated.......if it turns out to be the head.......well I am gonna have to buy a new head and install myself
since there is no way I can afford $3kto $4k........

Any ideas on where I can find original parts etc would also be appreciated.

Thanks in advance for any ideas/thoughts/suggestions. Ken
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Re: Rough Idle

Postby Mark » Sat Nov 21, 2009 9:05 pm

First, welcome to HXC and congratulations on your H3.

My first thought would be the head issue but also like you mentioned it would be a bit unusual for it to happen at the miles you have. I will try to check the service manual later to see if I can get the procedure for the compression test.
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Re: Rough Idle

Postby KGFORD » Sat Nov 21, 2009 9:12 pm

As a side note.....the error I am seeing is P0302......as read from the Autozone.
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Re: Rough Idle

Postby Mark » Sat Nov 21, 2009 10:14 pm

Engine compression test

Tools Required
J 38722 Compression Tester

Important: The battery much be at or near full charge. Do not block the throttle open.

1. Remove the air duct from the throttle control module.
2. Remove the ignition control module.
3. Disable the fuel system.
4. Remove the spark plugs.
5. Measure the engine compression, using the following procedure.
5.1 Firmly install J 38722 to the spark plug hole.
5.2 Have an assistant crank the engine through at least four compression strokes in the testing cylinder.
5.3 Check and record the readings on J 38722 at each stroke.
5.4 Disconnect J 38722
5.5 Repeat the compression test for each cylinder.
6. Record the compression readings from all of the cylinders. A normal reading should be approximately 1482 kPa (215 PSI).
The lowest reading should not be less than 70 percent of the highest reading.
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Re: Rough Idle

Postby KGFORD » Sat Nov 21, 2009 10:28 pm

Thanks for the info.

I went and cross referanced the Coil Ignition module from Autozone using google and it is the same part.
Colorado and H3 use the same Coil Ignition.

Even better news is that after confirming that, I went ahead and ran back down to Autozone and picked the
Coil/Ignition Module and installed.

H3 idles smooth as silk!!!!

Thank god since I was dreading that the issue was going to be the head.
Looks like it was just a bad ignition coil on Cyl 2. Had them clear the error code and will monitor over the next
couple of days but it idles smooth withg zero miss-fires and stumbling at idle. Smooth acceleration up as high as
4k to 5k rpm's

Thanks again for looking up the compression testing procedure.



H
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Re: Rough Idle

Postby Mark » Sat Nov 21, 2009 10:55 pm

Nice work on figuring out the issue, congratulations and enjoy 8)
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Re: Rough Idle

Postby alrock » Sat Nov 21, 2009 11:14 pm

Great news. Glad it was a pretty straightforward fix. Your posts will be really helpful for others down the road too.
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Re: Rough Idle

Postby c3 rolling » Sun Nov 22, 2009 12:01 am

Wow, fixed it on the second try! 8) . I recomend buying the AC Delco plugs though.
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Re: Rough Idle

Postby KGFORD » Mon Nov 23, 2009 3:50 pm

Speaking of Spark Plugs......anyone know what the Gap is supose to be?
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Re: Rough Idle

Postby c3 rolling » Mon Nov 23, 2009 11:57 pm

I believe .044
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Re: Rough Idle

Postby Mark » Tue Nov 24, 2009 8:04 am

Pretty much close enough :up: :yup: :lol:

Just checked the service manual this morning and it says 1.08mm or 0.042".
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Re: Rough Idle

Postby KGFORD » Wed Nov 25, 2009 12:57 pm

Thanks for the update on the Plug gap. Not sure if the differance between .042 and .045 would make any differance.
I would assume that you would "preferably" want a larger gap ( That you could get away with ) for a cleaner burn but who knows......

Sorry, dont want to turn this into a Spark Plug debate......do appreaciate the feed back though on what the Maint Manuals say they need to set at.

Thanks again, Ken
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Re: Rough Idle

Postby Mark » Wed Nov 25, 2009 1:07 pm

KGFORD wrote:Thanks for the update on the Plug gap. Not sure if the differance between .042 and .045 would make any differance.

Yeah, pretty much that it was close enough myself :yup:
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Re: Rough Idle

Postby Chief » Mon Apr 26, 2010 5:39 pm

Mark wrote:Engine compression test

Tools Required
J 38722 Compression Tester

Important: The battery much be at or near full charge. Do not block the throttle open.

1. Remove the air duct from the throttle control module.
2. Remove the ignition control module.
3. Disable the fuel system.
4. Remove the spark plugs.
5. Measure the engine compression, using the following procedure.
5.1 Firmly install J 38722 to the spark plug hole.
5.2 Have an assistant crank the engine through at least four compression strokes in the testing cylinder.
5.3 Check and record the readings on J 38722 at each stroke.
5.4 Disconnect J 38722
5.5 Repeat the compression test for each cylinder.
6. Record the compression readings from all of the cylinders. A normal reading should be approximately 1482 kPa (215 PSI).
The lowest reading should not be less than 70 percent of the highest reading.




I am having this same problem but i have an '07 with 63,000 and change on it.
I was plannign on changing the plugs to see if this would fix it and then change the coil. but if that does not work out for me i was going to check the compression but how do you disable the fuel system?
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Re: Rough Idle

Postby jens » Fri Apr 30, 2010 12:15 am

Hello,
if you pull fuse #3, you'll disable the fuel-pump.

regards,

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